SOLVED 03 Silverado 1500 5.3 LS. No crank no start no communication with ODB port but has power. Also the gear selector isn’t showing the line anymore.

[chadryanh]

I have a 2003 Silverado 1500 5.3 L. I recently installed a rebuilt 4L60E transmission in the truck. Before the replacement my truck started just fine, just had burnt clutches. Once everything was put back together I go to start the truck and it doesn’t want to crank. All light come on except gear selector on dash. I go to hook up a ODB reader and it will power on but when I try to run diagnosis it says no communication. I checked all fuses and relays. Tried to jump starter snd crank relays to see if it would start and never started. It did try and crank though. Checked voltage to starter and I’m getting 12 volts. Just put a new battery in as well. I replacer gear shifter solenoid and neutral safety switch thinking that might be the problem. Checked all connections on harness and tried checking all grounds. When I got this trans the safety neutral switch had the one plug for the harness. My harness has two plugs for it. Idk if that could be a problem and it’s not reading what gear it’s in or what. I feel like I’ve tried everything I know that I can do. Any guidance would be appreciated. This is the second transmission I’ve installed in my truck. First one had no problems after install. Could it be a security feature that’s stopping me from starting the truck maybe? One other thing I noticed it my key fob isn’t unlocking snd locking my truck anymore. Might be irrelevant but thought I’d throw it in.

Edited December 2, 2022 by chadryanh

[richard wysong]

There have been a few posts of very similar problems but no common fix that's been posted. I would start by checking all fuses both fuse boxes and power points with a test light to make sure there is power where there should be, also do voltage drop tests on the body and engine grounds. It could be a communication problem between the PCM and the BCM as well possibly caused by a bad ground in the serial data wiring. There are ground wires on the rear of the engine that may have been disturbed or broken changing the trans. I had a friends truck do almost the exact same thing after he changed the starter and battery but I got lucky and disconnecting the battery for an hour or so and connecting it with the key on fixed it. As stated I got lucky. PLEASE when you find the problem post the cause and cure

[richard wysong]

did you change it to the correct neutral switch? Those connectors can be a bear to unplug and plug in so you might want to check for broken/bent pins

[It's Tim]

50 minutes ago, richard wysong said:

disconnecting the battery for an hour or so and connecting it with the key on

[chadryanh]

I’ve checked all fuses and relays already. Safety neutral switch is the correct one also. I checked wires and pins to the plugs going to switch, everything looked good. One thing I did forget to mention on my original post was after I try to start the truck and then turn the key off and take the key out of the ignition all the dash lights and headlights continue to stay on so I have to disconnect the battery terminal to get them to go off. 

[richard wysong]

yeah, that's pointing to a problem with the Bcm communication

[chadryanh]

I figured out my problem. It was the electrical ground that ties into the back of the engine block by cylinder #8. When I was trying to maneuver my trans dipstick tube back to the trans I had to have broke it then. I Crimped the broken ground wire and ran it to a bolt on the front of the engine. 5 minutes to fix and started right up.

[richard wysong]

Thank You for posting the results How is your new tranny?

Edited December 4, 2022 by richard wysong

[chadryanh]

Truck is running great! Feels good to not have to worry with it for now. I’m pretty sure the ground ties in with the same ground tying into trans. From what I’ve seen.